Millimeter-Wave Mobile Broadband (MMB) system is a millimeter wave based system which operates in a radio frequency range of 30 Gigahertz (GHZ) and 300 GHz. MMB system uses radio waves with wavelength in range of 1 millimeter (mm) to 10 mm and is a candidate for next generation mobile communication technology due to considerable amount of spectrum available in mmWave band.
Generally, in a MMB system, MMB base stations are deployed with higher density than macro-cellular base stations in order to ensure good network coverage. This is possible as transmission and reception of signals is based on narrow beams which suppress interference from neighbouring MMB base stations and extend the range of an MMB link.
Typically, in a MMB network, multiple MMB base stations form a grid with a large number of nodes with which a mobile station can communicate, thereby ensuring high quality equal grade of service (EGOS) irrespective of the location of the mobile station. The grid having a plurality of MMB base stations serving a mobile station is commonly termed as virtual cell or cloud cell. In a cloud cell, the multiple base stations communicating with the mobile stations need to perform downlink transmission beamforming while the mobile stations communicating with the base stations need to perform downlink reception beamforming for receiving downlink control information and data packets. Similarly, a mobile station communicating with a base station in a cloud cell may need to perform uplink transmission beamforming while the base station needs to perform uplink reception beamforming for transmitting uplink data.
Further, in a cloud cell, one of the base stations acts a master base station and remaining base stations acts slave base stations with respect to the mobile station. In overlapping cloud cell scenario, a base station can be a part of more than one cloud cells. In one cloud cell, the base station acts as a master base station for one mobile station and in another cloud cell, the base station act as a slave base station for another mobile station.
In a conventional cellular system, in which a mobile station communicates with a single base station, the base station receives data packets from the IP network via data gateway in downlink, performs Medium Access Control (MAC) and Physical (PHY) processing of the data packets and transmits physical burst carrying the processed data packets to the mobile station. In the uplink, the base station receives physical bursts from the mobile station, performs PHY and MAC processing of the physical bursts, and transmits data packets to an Internet Protocol (IP) network via the data gateway.
In another conventional cellular system, in which a mobile station communicates with a base station via a relay station, the base station receives data packets from the IP network via data gateway in downlink, performs MAC processing of the data packets and transmits MAC Protocol Data Units (PDUs) to the relay station. The relay station performs PHY processing of the MAC PDUs and transmits the physical bursts carrying the MAC PDUs to the mobile station. In the uplink, the relay station receives the physical burst from the mobile station, performs PHY processing of the physical burst and transmits the MAC PDUs received in the physical bursts to the base station so that the base station transmits the data packets containing the MAC PDUs to the data gateway.
However, in a cloud cell environment, since multiple base stations are grouped together to serve a mobile station and the mobile station communicates with multiple base stations in a cloud cell, it is desirable to address problems associated with routing data packets from the IP network to the mobile station through the base station(s) in the cloud cell, processing of data packets across the base station(s) in the cloud cell in downlink and uplink and routing data packets from the mobile station to the IP network through the base station(s) in the cloud cell.